In electrical power systems, fault, status and meter data are used to verify proper operation of the power system, control the system and detect transmission lines faults. The system parameters typically measured are: phase voltages (VA, VB and VC), phase currents (IA, IB, and IC), line power levels (PA, PB and PC) and reactive power level (QA, QB and QC). Manual and automatic systems monitor these quantities to control the power system.
Often, one power system in one geographic location may be tied to a second power system at a remote location. Generally, one system is located in an area of high-power generation while the other system is located in an area of high-power consumption. For example, the Pacific AC Intertie connects the Bonneville Power Administration (BPA) system in the Northwest to the Pacific Gas and Electric (P.G.&E.) system in Northern California.
On such systems, if a disturbance occurs for which stability cannot be maintained, one system, e.g. the BPA, can signal the second system, e.g. P.G.&E., to separate at a certain point. This may be done by a microwave transfer trip signal with audio tones. In certain cases, the separation signal may be accidently or inadvertently generated, resulting in an unwarranted separation of one system from the other. For example, such inadvertent separation may occur as a result of a maintenance or testing error. Such unwarranted separation is obviously expensive, troublesome, and undesirable. Thus, preferably, a backup system is provided to prevent unwarranted separation.
Accordingly, an object of the present invention is to provide a system for detecting system disturbances and qualifying system-separation transfer-trip commands in order to prevent unwarranted separation of one power system from another.